1. Technical Field
The present invention relates to a quantum interference unit, a quantum interference device, an atomic oscillator, an electronic apparatus, and a moving object.
2. Related Art
An atomic oscillator which oscillates on the basis of energy transition of atoms of an alkali metal such as rubidium or cesium is known. Generally, the operating principles of atomic oscillators are roughly divided into a system utilizing double resonance of light and microwaves and a system utilizing a quantum interference effect (CPT (coherence population trapping)) of two lights with different wavelengths.
In an atomic oscillator of either system, an alkali metal is enclosed in a gas cell, and the gas cell needs to be heated to a predetermined temperature in order to maintain the alkali metal in a gaseous state. Also, in general, the gas cell is housed in an airtightly sealed package, and a coil for applying a steady magnetic field to the alkali metal inside the gas cell is provided for the purpose of improving the oscillation.
For example, the atomic oscillator according to JP-A-2012-191523 has a package formed of a base material of kovar that is Ni-plated on the surface. The atomic oscillator according to JP-A-2013-3139 has a package formed of a non-magnetic ceramic.
However, in the atomic oscillator according to JP-A-2012-191523, since the package is formed with a ferromagnetic material, the package is magnetized by the magnetic fields from the coil and from the outside. Therefore, the magnetic field acting on the alkali metal in the gas cell changes which causes a problem of frequency stability deterioration. Meanwhile, since the package is non-magnetic in the atomic oscillator according to JP-A-2013-3139, the foregoing problem does not occur. However, since the ceramic has a high radiation heat absorptance, a great amount of heat escapes to the outside from inside the package which causes a problem of increased power consumption.